In 2004, 10.6% of adolescents in the U.S. between the ages of 12 and 17 reported using drugs in the past month. This translated to an estimated 1.5 million adolescents in need of treatment for alcohol use and 1.4 million adolescents in need of treatment for illicit drug use. Considering the significant personal suffering and widespread social burden associated with drug addiction, accurately characterizing motivational processes during adolescence is critical to developing an enhanced understanding of why adolescents engage in high risk activities such as using and abusing drugs and ultimately developing targeted prevention programs. In this regard, there is substantial cause for optimism. Researchers have made significant conceptual and empirical strides in characterizing the neurobiology of reward. Coupled with continuing advancements in functional neuroimaging, the growing field of developmental functional neuroimaging is poised to answer some of the most important questions faced by drug addiction researchers. A major advancement has been in the ability to consistently obtain strong activations in dopamine rich brain regions using functional imaging and these activations may serve as important biomarkers of developmental differences in reward processing. However, the validity of such comparisons rests on establishing developmental continuity in how the brain processes rewards. The present study focuses on age differences in relative reward processing-that is, neural activations to reward cues in relation to alternative available rewards. In the fMRI task used in the present study, participants will have the opportunity to win or lose actual money by responding to cues associated with rewards and punishments. The central hypothesis of this study is that adolescents differ from adults in processing of relative reward value. The present study has two specific aims: 1) Establish how processing of relative reward value in the ventral striatum differs in adolescents and adults; 2) Determine how positive affect ratings towards gain cues correlate with anticipatory activation in the ventral striatum in adolescents and adults. This application represents an important step in characterizing developmental changes in processing of rewards in order to characterize adolescent motivational processes. Based on the results of this study, future investigations will focus on how reward sensitivity and coding of reward value differentially predict impulsive behavior in children, adolescents, and adults. Furthermore, analyses will be conducted to determine how maturation of prefrontal cortex structures influences reward activity, including relative reward processing, in the ventral striatum. Developmental changes in sensitivity to rewarding stimuli may account for why adolescents use and abuse drugs. This study will use functional neuroimaging to characterize how adolescent and adult brains respond differently to rewards. Based on this research, it will be possible to develop prevention and treatment programs that take into consideration motivational processes that may be unique to adolescents. [unreadable] [unreadable] [unreadable]